Variations in the content of the enzyme lysozyme have been detected in various body fluids and tissues. Many of these variations have been correlated with certain body functions and/or malfunctions or diseased states. For example, it has been reported in the medical literature that elevated levels of lysozyme in serum and/or urine have been shown to be coincidental with megaloblastic anemia, monocytic and monomyelocytic leukemia, polycythemia vera, and acute myelogenous leukemia. Further, the lysozyme concentration has been shown to be elevated in the synovial fluid of patients with rheumatoid arthritis. During pregnancy because lysozyme is not indiginous to the vaginal cavity the mere presence of lysozyme in vaginal fluid is accepted as an indicator of the presence of amniotic fluid in the vagina because lysozyme is known to be a constituent of the amniotic fluid. If lysozyme is therefore found in the vaginal fluid it can be taken as an indicator that a rupture has occurred in the amniochorial membranes. From these facts it is clear that a reliable, rapid, facile and inexpensive lysozyme assay would be useful as a clinical diagnostic tool.
The research scientist has at his disposal many sophisticated machines and techniques to help him determine enzyme concentrations in various fluids. Certain of these machines or techniques have been used to assay lysozyme in biological fluids and tissues. These techniques and machines, however, are not suitable for routine clinical use for one or more of the following reasons: the technique is too slow; the technique is often cumbersome to perform; the technique requires the purchase of and maintenance of expensive equipment which also necessitates having available experienced technicians; the technique or the tool requires too large an amount of test tissue or biological fluid as well as other associated factors.
In Identification of a Bactericidal Factor (B-Lysin) in Amniotic Fluid at 14 and 40 Weeks Gestation, 788, No. 7, Volume 127, Am. J. of Obstetrics and Gynocology, 1977, I described a technique for determining the lysozyme concentration in an amniotic fluid. While this technique is useful for detecting lysozyme in amniotic fluid it is not susceptible to broad clinical use because of the equipment necessary in performance thereof.
A clinical method for determining the lysozyme content in human tears has been described by B. Bonavida and A. T. Sapse in Human Tear Lysozyme, 66, Am. J. of Opthal., 70 (1970). The Bonavida technique utilizes the action of lysozyme on the cell walls of Micrococcus lysodiekticus. The M. lysodiekticus is suspended in an agrose solution made up in a sodium chloride and sodium phosphate buffer which also contains sodium azide. Detection of the lysozyme action on the cell walls of M. lysodiekticus using this technique requires incubation at 37.degree. C. for 24 hours. This technique requires at least a minimum period of four hours to even observe the first sign of lysis caused by the lysozyme and the before mentioned 24-hour incubation period to assure reliable results.
In many clinical situations wherein a lysozyme assay would be useful as a diagnostic tool this 24-hour incubation period essentially negates the possibility of using this assay. For example, if rupture of the amniochorial membranes should occur infection of the fetus may result. In the present clinical management of such a rupture it is considered best to initiate either delivery of the fetus or appropriate antibiotic treatment of both the fetus and the mother at at least 12 hours and no later than 16 hours after rupture. The 24-hour incubation period of the Bonavida technique therefore renders this technique inappropriate in this clinical situation.